Scientists at the Technical University of Denmark (DTU) have confirmed the physics underlying the newly discovered phenomenon of magnetic levitation.
In 2021, Turkish scientists published a research paper detailing an experiment in which they attached magnets to motors to make them spin faster. When I brought this setup closer to her second magnet, the second magnet started spinning and suddenly came to rest in a fixed position a few centimeters away.
Magnetic levitation is not new, but perhaps the most well-known example is maglev trains, which rely on strong magnetic forces for lift and propulsion. This experiment baffled physicists because this phenomenon was not explained by classical physics, at least by any theory. The mechanism of magnetic levitation is known.
We demonstrated magnetic levitation using a Dremel tool that rotates a magnet at 266 Hz. The rotor magnet is 7x7x7mm3 and the floater magnet is 6x6x6mm3. This video shows the physics explained in the study. Credit: DTU.
But it is now. Rasmus Bjørk, a professor at DTU Energy, was intrigued by Ucar’s experiment and decided to recreate it with his master’s student Joachim M. Hermansen, knowing exactly what was going on. I have started. Although replication was easy and could be done using off-the-shelf components, its physics were strange, says Rasmus Björk.
“Magnets shouldn’t float when they’re close to each other. Normally they attract or repel each other. But we found that we could achieve this hovering by rotating one of the magnets.” That’s the strange part: rotating one of the magnets shouldn’t change the force acting on it, so there seems to be a correlation between movement and magnetic force.” he says.
The results were recently published in the journal physics review applied.
Some experiments to confirm the physics
The experiment used several magnets of different sizes, but the principle was the same. By spinning the magnet so fast, the researchers observed how another nearby magnet, called a “floater magnet,” began to rotate at the same speed and quickly became fixed. Position that remains hovering.
They found that when the floater magnet is locked in place, the floater magnet is oriented close to the axis of rotation and toward similar poles of the rotor magnet. So, for example, the north pole of a floater magnet will remain pointing towards the north pole of a stationary magnet while it rotates.
This is different from what would be expected based on the magnetostatic laws, which describe how magnetostatic systems work. But as it turns out, the magnetostatic interaction between rotating magnets is precisely what creates the equilibrium position of a floating body, as co-author doctoral student Frederick L. Durfus discovered using simulations of the phenomenon. It turned out that it was. They observed that the size of the magnet had a significant effect on the levitation dynamics. Smaller magnets have more inertia and higher levitation forces, thus requiring higher rotational speeds for levitation.
“The floater magnet wants to align itself with the rotating magnet, but we find that it cannot rotate fast enough to do so. And as long as this coupling is maintained, it will hover or float. ” says Rasmus Björk, adding:
“It might be likened to a spinning top. If it’s not spinning it won’t stand on its own, but the rotation will lock it in place. It’s only when the rotation loses energy that gravity, or in our case a magnet, The push and pull of becomes large enough to overcome equilibrium.”
Reference: “Magnetic levitation by rotation”, by Joachim Marko Hermansen, Frederik Raust Dolphs, Catherine Fransen, Marco Belleggia, Christian R.H. Bahr, and Rasmus Björk, October 13, 2023 , Physical review applied.
DOI: 10.1103/PhysRevApplied.20.044036